This post continues the discussion of the National Academies of Sciences management of Legionella in water systems report. Chapter two begins to delve into the diagnosis, ecology, and exposure pathways of Legionella. In our everyday life, humans live peacefully alongside a number of microbes, organisms so small they are invisible to the human eye. Most of these microbes are harmless and may are beneficial. However, there are groups of microbes that cause disease In general, the impact of exposure to a particular microbe depends on three factors. Firstly, the quantity of microorganisms. Secondly, their capacity to cause harm. Lastly, the strength of an individual human’s defenses. The scales are skewed towards infection when the microbes find and enter a susceptible host. Studies around the world have shown increasing incidence of Legionella cases. This can be attributed to many factors. The first is changing demographics, such as the aging population. This may contribute to the rise in disease incidence as well. From 1970 to 2018, the median age in the United States has increased by nearly ten years, such that Americans aged 65 and older now make up a larger portion of the U.S. population Likewise, the number of individuals that are considered immunocompromised has increased. This is due to the widespread use of immunosuppressive therapies. Additionally, the prolonged survival among higher-risk immunosuppressed patients may contribute to increasing legionellosis incidence. Current data suggest that at least 2.7 percent of Americans consider themselves immunosuppressed. In other words, nearly 9 million at-risk individuals in the United States by this criterion alone. Patients with known impaired immune function, including those suffering from organ failure are at a higher risk. Patients undergoing treatment for cancer and those who have received a solid organ transplant may be at highest risk because of the depth and length of immunosuppression required. Another population vulnerable to Legionella pneumonia is patients at increased risk of aspiration, such as those with neuromuscular diseases, the elderly, and infants. Furthermore, increasing population density in cities is a risk factor. These growing populations that live in cities are served by aging, centralized water systems may elevate the risk of legionellosis. There is also an exponential growth of water towers being added to cities infrastructure. In fact, American Society of Civil Engineers gave the U.S. water infrastructure a “D” rating. As a result, exposure in daily life may be more frequent due to the increased population and aging water infrastructure. The day to day interactions with water products and water devices, particularly those ideally suited for Legionella growth (e.g., cooling towers; hosing, faucets, and showerheads; hot tubs, Jacuzzis, and spas; humidifiers; fountains). This highlights the immediate need for an update to the nations way of managing Legionella. [1] Click here for a free consultation! THE MATERIALS ON THIS WEBSITE HAVE BEEN PREPARED BY JULES ZACHER, P.C. FOR INFORMATIONAL PURPOSES ONLY AND ARE NOT LEGAL ADVICE OR A SUBSTITUTE FOR LEGAL COUNSEL. [1] https://www.nap.edu/catalog/25474/management-of-legionella-in-water-systems